This invention relates generally to a system for providing an indication to a vehicle operator of the miles a vehicle has the capability of traveling relative to the amount of fuel remaining for the operation of the vehicle at the time of the calculation, and more particularly, relates to a system for providing an instantaneous indication of the true miles to go for a vehicle under any operating conditions and an indication of how the true miles to go varies with variations in operating conditions of the vehicle.
In operating a motor vehicle, the situation has often arisen where the operator desired to know the number of miles which the vehicle is capable of traveling with the remaining quantity of fuel on board the vehicle. This calculation has been typically made by estimating the amount of fuel remaining in the vehicle, estimating the amount of fuel consumption for the particular speed at which the vehicle is being operated and multiplying the fuel consumption in miles per gallon by the remaining quantity of fuel on board to arrive at an estimated miles to go figure. However, at best, this figure is an estimate and could result in gross inaccuracies. Further, while the operator may vary the operating conditions of the vehile to maximize the remaining miles to go within the limits of operation of the highway on which the vehicle is being operated, the operator has no accurate measure of maximizing the miles to go.
Accordingly, if a vehicle is low on fuel and the operator knows the distance to the next fueling station, it would be desirable to operate the vehicle to provide a fuel consumption which is consistent with the conditions of the highway on which the vehicle is being operated and also to provide an operation which will insure that the vehicle will have sufficient fuel to travel to the next fueling station. Also, it would be desirable to provide a fuel consumption indication in order to facilitate the operator maximizing the fuel consumption of the vehicle irrespective of the requirement to know the miles to go capability of the vehicle for the fuel on board.
A system has previously been evolved which provides an indication to the driver of the amount of fuel being consumed by the vehicle based on either the distance traveled or the lapsed timed. In this arrangement, described in U.S. Pat. No. 3,812,710, issued May 28, 1974 and entitled "Electronic Fuel Consumption Meter, " certain engine operating parameters are sensed, for example engine drive shaft speed and throttle setting, or rotational speed and the pressure in the intake manifold or the pressure in the intake manifold and the setting of the throttle valve, and are utilized to provide an electrical output that is calibrated to read fuel consumption in unit distance or fuel consumption in unit time for the travel of the vehicle.
The system described in the above described patent does not provide the operator with an output signal which is indicative of the true miles to go of the vehicle for the fuel available on board. Also, the system disclosed does not describe the particular manner in which the system of the instant invention derives a fuel consumption signal to enable the operator to maximize the fuel consumption without regard to the number of miles remaining to go for the vehicle.
The system of the present invention provides a transducer for sensing the vehicle speed which may either be in an analog or digital form. If the signal is an analog form, the signal is suitably amplified and fed to an analog divider circuit. If the signal is in digital form, the signal is conditioned through an integrator circuit and an active filter circuit which provides an analog signal representative of the vehicle speed under all vehicle operating conditions. The system also includes a sensor for providing a signal indicative of the fuel consumption of the vehicle. In the case of a fuel injected engine, this signal is easily derived by sensing the pulses being fed to the fuel injector or injectors, as the case may be, and integrating this signal by means of a signal conditioner to provide an analog signal representative of fuel consumption of the vehicle.
The vehicle speed signal is then fed to an analog divider which divides the vehicle speed signal by the fuel consumption signal to provide a fuel consumption signal calibrated in distance traveled per quantity of fuel. This signal is then fed to a multiplier circuit through a buffer, the multiplier circuit including an input from a quantity of fuel sensor which provides an indication of the remaining quantity of fuel on board the vehicle. The output of the buffer is multiplied by the quantity of fuel remaining signal which then provides an output signal representative of the remaining miles to go capability of the vehicle. The system also includes an inhibit switch to provide the output signal only during high gear operation of the vehicle to insure that spurious signals are not generated during rapid acceleration or deceleration situations, which signals would not be useful to the operator.